If a child's parent is physically abusive, is the child in the right to physically defend themselves?

Tw: abuse

So I'm asking this question because growing up my mother was very emotionally and physically abusive to me and my dad. I tried seeking help from my elementary school (to which the conselar said that mothers can't be abusive), and the police were called multiple times, but she never once got in actual trouble. When I was in about 4th grade she gave me a concussion from hitting my head on the kitchen floor and when the police were called she tried to blame my father.

My grandmother always told me that anytime she started to hit me I should hit her back harder. As a child I listened and even busted her nose once when she attacked me. Thankfully, she kicked me out when I was 13 and I was able to get away from the violence. When I was 16 I saw her again and she actually got arrested after she punched me in the face and my BF called the police, but the only reason they arrested her was because there were multiple witnesses.

So, do you think it's justified for a child to fight back against abuse? What do you think the outcome and effects are?